The present invention relates to a stable, ruby red natural colorant, and more particularly, to colorant derived from purple sunflower hulls. The stable, red natural colorant is useful as a coloring agent in food products, cosmetics, pharmaceuticals and other materials. The invention further relates to a method of making such red colorant.
The publications and other materials, used herein to illuminate the background of the invention or provide additional details respecting the practice, are each hereby incorporated by reference, and for convenience the full citations are respectively listed, as follows: Fox, G. J. and Dreher, M. L. 1982. "Extraction of anthocyanins from sunflower hulls". North Dakota Farm Research 40(1):3-6; Fox, G. J. et al. 1986. "Survey of anthocyanin content of purple hulled sunflower entries within the USDA World Collection of sunflower". In Proc. Sunflower Research Workshop Dec. 10, 1986. p. 5; Fox, G. J. et al. 1989. "Anthocyanin quantity, quality and stability in a purple hulled hybrid derived from Neagra de Cluj". In Proc, Sunflower Research Workshop Jan. 9 & 10, 1989. pp. 17-18; Fuleki, T. and Francis, F. J., 1968. "Quantitation methods for anthocyanins". J. Food Sci. 33:72-78; Gao, L. and Mazza, G. 1996. "Extraction of anthocyanin pigments from purple sunflower hulls". J. Food Sci. 61(3):600-603; Mazza, G. and Miniati, E. 1996. "Anthocyanins in Fruits, Vegetables and Grains" CRC Press, Ann Arbor, Mich. pp. 312-313: Metivier, R. L., et al., 1980. "Solvent extraction of anthocyanins from wine pomace". J. Food Sci. 45:1099-1100; Mok, C. and Hettiarachchy, N. S., 1991. "Heat stability of sunflower hull anthocyanin pigment". J. Food Sci. 56:553; Riboh, M., 1977. "Natural colors: what works . . . what doesn't". Food Engr., May:66-72; Woo, A. H., et al., 1980. "Anthocyanin recovery from cranberry pulp wastes by membrane technology". J. Food Sci. 45:875-879: and U.S. Pat. No. 4,172,902.
There has been much interest in use of natural colorants, for example in food products, in part due to the delisting by the U.S. Food and Drug Administration of the certified dyes, red dye #2 and red dye #4. Compared to certified dyes, some of the natural colorants are less useful because they are not as temperature and light stable as desired. One such natural colorant which has been used in food products is anthocyanin, the primary natural colorant of fruits. Grape, cranberry and red cabbage extracts are commonly used as anthocyanin based food colorants. Anthocyanins derived from grape skins have been used to fortify the coloration of wines and other food products, but the pigment yield is relatively low (Metivier, et al., 1980). Cranberry extracts are a useful source of anthocyanin, however yield is very low (Woo, et al., 1980). Furthermore, these sources of anthocyanin are expensive to obtain and often unstable, loosing color upon exposure to light, temperatures above 26.degree. C., and at pH levels above 3.0.
Purple hulled sunflower, in which red anthocyanins are concentrated in the hull, are a relatively inexpensive potential source of red anthocyanin. According to Mok and Hettiarachchy (1991), minimum degradation and maximum extraction of anthocyanins from sunflower hulls should be carried out at room temperature using aqueous SO.sub.2 solution at a concentration of 1000 ppm. It is well known that sunflower anthocyanins are a brightly colored ruby red when in solution at a pH below 3. However, they quickly lose (red) color and stability as pH is raised with complete color loss as pH is raised above pH 7. It has also been previously reported that sunflower anthocyanins lose color in the presence of light or heat (above 26.degree. C.) (Mazza and Miniati, 1996). Fox and Dreher (1982) have reported that anthocyanin production in sunflower hulls is controlled by two major dominant genes; one directs anthocyanin production in the sunflower plant and the other directs the translocation of anthocyanin into the hull tissue. Fox, et al. (1986) have reported that additional genetic and environmental factors can result in anthocyanin hull percentages ranging from 0.1% to 3.0%.
Certain organic compounds have been shown to stabilize anthocyanins through acylation of the anthocyanin molecule. One such example is "Heavenly Blue" Morning Glory, peonidin 3-(dicaffeylsophoroside)-5-glucoside, which is a naturally occurring anthocyanin acylated with caffeic acid (Asea, et al., U.S. Pat. No. 4,172,902). Limited acylation of sunflower anthocyanins has been reported, with chlorogenic acid being the primary acylating agent (Fox, et al., 1989).
There have been no reports, to date, of sunflower anthocyanin extraction techniques which provide anthocyanin stability over a wide range of pH and exposure to light. Neither has there been any reports of extraction techniques which employ elevated temperatures or result in a colorant which is stable at an elevated pH.